This is how I do it

not saying it's right, but it works for me.
I like to make my pillowcases on the serger.  It is fast and all those little feathery things are not left on the pillowcase when I make it the old way with french seams.  (I know some of you are going to object to me saying the "old way".)
Step by step.....here we go.
After I have cut the length of the body and the cuff I lay the cuff piece on top of the body piece and cut both at the same time. I leave them folded in half and pull that folded side over to the "0" mark on my cutting mat.  I lay the ruler on the 20.5 mark on the mat and zip goes the rotary cutter.  If I have an insert piece I place that on the body of the pillowcase too.  I don't stack it on top of the cuff, just on the body piece.  Too many pieces when stacked together can cause inaccurate cutting.

I'm a bit fussy when it comes to directional fabric.  I like the -- cats in this case -- to face out to the edge, not in to the body.  I lay the cuff right side up on the cutting table, then lay the body of the case right side down and pin a few spots.

Then I flip the larger piece over to see if the cuff is the right way.

If it is, I go ahead and do the "roll up" method for the pillowcase placing the pins well away from the edge of the case.  

I don't want to have to stop and start to remove them and DO NOT ever run over a pin with the serger.

Yes, it's another Husqvarna!

When this is done, I take the case to the ironing board and press the cuff along the edge so that it lays flat.  I do it from the right side and from the inside.
Back to the serger and I pin way out again and sew the top seam, right sides together, from the open side to the fold. I leave long tails of serger thread.
I'm sorry the next photo is blurry.  I took this shot about 10 times and never got a clear photo.  I don't know what happened to "old faithful" but she failed me on this one.
I place a pin right where the cuff meets the body of the pillowcase.  I really want that join to meet.
I start at the cuff and work my way up to the top seam.

 When I'm finished I tie the threads off.  I find the two straight stitch threads and pull them out of the overcast stitches.  I tie them left over right, right over left.  Thank goodness for Girl Guides!  Then I fray check them.  They will never become unravelled.

Back to the ironing board for the final pressing.
Ta-Da ~~ all done! Length of time..........less than 20 minutes and I was taking photos along the way!